Rotary actuators such as rotary motors and rotary pumps commonly utilize a rotor which includes a vane which extends radially from a shaft into a liquid-filled chamber into which a fixed stator vane or blade extends in a radial direction. In the case of a pump rotation of the rotor from an external drive forces liquid from the leading side of the rotor vane to the trailing side through an external conduit including a load. In the case of an actuator or motor, liquid is pumped into the chamber on one side of the rotor vane which thus imparts a torque to the rotor causing angular movement thereof. One such rotary actuator is described in detail in U.S. Pat. No. 4,495,856.
A major problem which is inherent with these types of devices is the leakage of the hydraulic fluid around the edges of the rotor vane from the high pressure side to the low pressure side of the chamber, and the most troublesome leakage area is at the corners of the vane where it adjoins the shaft and the associated housing. Extremely small dimensional tolerances must be maintained, and this has resulted in relatively high manufacturing costs.